The present invention relates to an improvement in the method of making a mesa type thyristor and the constitution of the thyristor made by the method.
Hitherto, there have been known mesa type thyristors, having a mesa surface along the periphery of a semiconductor substrate for attaining a high reverse breakdown voltage. However, such a mesa portion is likely to inudce an inversion layer (i.e. channel region) when sodium ions are adsorbed thereon.
In thyristors, wherein P-N junctions are formed near respective surfaces, an inversion layer allows a leakage current to flow therethrough across the P-N junctions and makes it difficult to attain the intended high reverse breakdown voltage. Such a shortcoming due to the inversion layer is liable to occur when a semiconductor substrate of very high specific resistivity is employed for making a thyristor with a high reverse breakdown voltage.